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Shadow copies of the EXT2 superblock

Posted: Mon Feb 17, 2014 10:59 pm
by eryjus
I apologize for the silly question. I have been studying the following document: http://www.nongnu.org/ext2-doc/ext2.pdf
With the introduction of revision 1 and the sparse superblock feature in Ext2, only speciļ¬c block groups contain copies of the superblock and block group descriptor table. All block groups still contain the block bitmap, inode bitmap, inode table, and data blocks. The shadow copies of the superblock can be located in block groups 0, 1 and powers of 3, 5 and 7.
For whatever reason, I am not confident in my own brain today.... "... power of 3 ..." is stating "N cubed, where N == 1, 2, 3, 4, 5, ...", NOT "N * 3".

Also, my calculations tell me that there is a theoretical maximum of 262,144 block groups (2,147,483,647 / 8,192 for 1K blocks [rounded up]).

My brain tells me that my thinking above is correct, but something is nagging at me I cannot put a finger on.... Can someone please check my thinking above?


Thanks!!

EDIT: .... OR .... should I be thinking "3 to the power of N, where N == 1, 2, 3, 4, 5, etc..."

Re: Shadow copies of the EXT2 superblock

Posted: Mon Feb 17, 2014 11:27 pm
by gerryg400
Power of 3 means 3, 9, 27, 81, 243, 729 .... etc.
Power of 5 means 5, 25, 125, 625 .... etc.
Power of 7 means 7, 49, 343 ... etc.

Which gives 0, 1, 3, 5, 7, 9, 25, 27, 49, 81, 125, 243, 343, 625, 729 ... etc.

Re: Shadow copies of the EXT2 superblock

Posted: Mon Feb 17, 2014 11:48 pm
by eryjus
gerryg400 wrote:Which gives 0, 1, 3, 5, 7, 9, 25, 27, 49, 81, 125, 243, 343, 625, 729 ... etc.
Thank you so much!!!